Tube with metallic block and method of attaching latter



Feb. 28, 1939. Q CHAPMAN AL 2,149,008

TUBE WITH METALLIC BLOCK AND METHOD OF ATTACHING LATTER Filed Sept. 15,1957 INVENTOR Edward 6 fid vmalt lav/aim Zanaall Patented Feb. 28, 1939TUBE WITH METALLIC BLOCK AND METHOD OF ATTACHING LATTEB Edward O.Chapman, Lookout Mountain, and John F. Randall, Chattanooga, Tenn,assignors tto gkongmtion Engineering Company, Inc., New

Application September 15,1937, Serial No. mam

9 Claims. (01. 122-6) In connection with furnace water walls there is ademand for tubes which are provided with metallic blocks on the sidefacing the furnace. The object of these blocks is to protect the tubesagainst the intense heat on the furnace side. In order that the blocksthemselves may be protected against becoming overheated, there must begood heat transfer between them and the tubes so that heat absorbed bythe blocks can be transmitted to the tubes and carried off by the watercirculating through them. No doubt the best means for assuring good heattransfer between the blocks and the tubes is to make the two integralwith each other as disclosed in United States Patent 1,732,514 grantedon October 22, 1929, to A. T. Hunter.

The present invention has for its object the provision of such blockssecured to the tubes by means which assure substantially as good heattransfer as in the patented form referred to, such means employed by thepresent invention however being less expensive than those employed bythe patentee.

The invention will be described in connection with the accompanyingdrawing in which Fig. 1 shows a portion of a tube with blocks secured toit in accordance with my invention; Fig. 2 is a section on line 2-2 ofFig. 1; Figs. 3 and a are views corresponding to Figs. 1 and. 2illustrating a variation; Figs. 5 and 6 are views likewise correspondingrespectively to Figs. 1 and 2 and showing a further variation, and Figs.'1 and 8 are two similar views showing another variation.

Referring first to the form of Figs. 1 and Z, the tube to which theblocks are secured appears at l, two blocks being shown at 3-3 inFig. 1. It will be understood that as many of these blocks are put oneach pipe as are required. The blocks are shaped similar to those usedin prior instances, resembling quite closely those of the patentreferred to above. Their flat side 5 will face the furnace in thecompleted installation and the blocks are of such size related to thespacing of the pipes that a substan tially continuous surface is formed.Adjacent blocks 33 on any given pipe are either in contact orsubstantially so. The blocks are formed with a curved surface 1corresponding to the curvature of the tube to which they are to besecured. This surface is either cast directly to the required form ormachined to such form.

In accordance with the present invention these blocks are brazed on thetubes, the material used being ordinary spelter or spelter of suchcomposition and melting point as seems indicated in any given case forthe service to which the tubes are intended. It has been found that theheat transfer from the block to the tube is entirely satisfactory withblocks brazed on as stated. There is, however, the difficulty that thebrazing material does not furnish sufllcient strength to keep the blockand tube from separating when stresses occur due to unequal heating, orfrom other causes, such as warping. To furnish the additional strengththe invention provides for welding theblock to the tube at certainpoints and over certain areas. In the form shown in Figs. 1 and 2 thereare provided two plug welds 9--9 for each block and two longitudinalwelds lll| along the lateral edges of the block.

In practice the blocks are first welded to the tube at 9--9 and ll-H,the brazing material is then placed into the openings |3--l3 providedfor this purpose, and the assembled tube and blocks are then placed in afurnace where they are kept at the proper temperature and for therequired time to effect brazing. 'Capillary attraction will cause themelted brazing material to flow into and fill even the smallest crevicesand cavities between the tube and the block. It may be desirable in someinstances to use a flux and in some instances it may further bedesirable to treat the surfaces of the tube and the block in one way oranother before the brazing operation. For example, it has been foundbeneficial to oxidize the surface of the block, if the block is made ofcast iron.

' While the temperature at which the brazing material melts is far belowthe melting point of the steel, this melting temperature of the brazingmaterial is not reached in service because the water flowing through thetube keeps the temperature at a point only slightly above thetemperature oi the water itself.

In the form shown in Figs. l and 2 there are indicated two openings 9-9and six openings i3l3. This of course is illustrative only. In somecases it may be sufficient to have a smaller number of such plug weldsand openings l3-i3 and in some cases more may be required. likewise, theparticular length of the block in the direction of the tube axis mayobviously be varied from that shown.

Instead of having circular plug welds 99 as in Figs. 1 and 2, anelongated weld 9', as shown in Figs. 3 and 4, will be found preferablein many cases. This is easier to weld than the circular plugs of Figs. 1and 2.

It will be understood that the primary object of the plug welds 9-9 andthe line welds H--l| is to furnish strength and to prevent the tube fromseparating from the plug; In some types of surface it will prove"sufficient to use only the line welds lll i. Such a case is illustratedin Figs. 5 and 6. v In that case the openings i3'l3' for theintroduction of the brazing material are preferably placed centrally asillustrated in these figures.

In Figs. 7 and 8 there is shown a variation in which the line weldsalong the sides are omitted, only the plugs 99 being used. In this casethe brazing material is placed either on the tube or along the edges ofthe blocks, and no feed holes I3 are used. The tube is placed into thefurnace in 'a position with the blocks below and the tube above. This isto prevent the brazing fluid from running out.

From the standpoint of avoiding rapid oxidation of the block, cast ironis a desirable material to use for the blocks. The openings for theintroduction of the brazing material and for the welding in of the plugscan in that case be either cored out or machined out. From thestandpoint of ease of welding the blocks to the tubes steel is apreferable material for the blocks. If made of steel, the blocks canalso be cast or they can be drop forged ormachined out of a largerpiece. Heat resistant steels may be used if desired. In case ordinarycarbon steel is used, it will be found necessary in most cases to coatthe blocks, particularly the exposed surface 5, with some oxidationresisting material. This can be applied by calorizing, spraying,dipping, electric plating, or other preferred means.

What we claim is:

1. In or for the wall or lining of a furnace, a tube, and a metallicblock having a. surface curved complementarily to a portion of the tubesurface, the complementary surfaces being united by brazing to providegood heat conductivity from the block to the tube, the block beingsecured to the tube further by welding to furnish strength to preventseparation from warping or difierentiai expansion,

2. Apparatus in accordance with claim 1, the Welding comprising a plugweld extending through the body of the block.

3. Apparatus in accordance with claim 1, the curved surface or" theblock terminating in two edges extending lengthwise of the tube, saidtwo edges being welded to the tube.

4. Apparatus in accordance with claim 1, the curved surface of the blockterminating in two edges extending lengthwise of the tube, said blockbeing welded to the tube along said two edges and also by means of aplug weld extending through the body of the block.

5. Apparatus in accordance with claim 1, the curved surface of the blockterminating in two edges extending lengthwise of the tube, said blockbeing welded to the tube along said two edges and also by means of aplug weld which extends through the block at its thinnest point andwhich is longer in a direction parallel to the length of the tube thanin a direction at right angles thereto.

6. In or for the wall or lining of a furnace, a tube, a plurality ofmetallic blocks each having a surface curved complementarily to aportion of the tube surface, the complementary surfaces being united bybrazing to provide good heat conductivity from the blocks to the tube,the blocks being arranged end to end along the tube and being furthersecured to the tube by welding to furnish strength to prevent separationfrom warping or difierential expansion.

7. The process of uniting to a tube a block of the kind describedcomprising the steps of shaping one surface of the block to fit thesurface of the tube, brazing said surface to the tube to provide forready heat transmission from the block to the tube, and welding theblock to the tube over sufficient area to provide strength to resist anytendency for the two to separate arising from the operating conditionsto which the structure is subjected.

8. The process in accordance withclaim 7 and further comprisingproviding a plurality of passages from said shaped surface of the blockto the opposite surface, the brazing material being introduced into saidpassages.

9. The process in accordance with claim 7 and further comprisingproviding a plurality of passages from said shaped surface of the blockto the opposite surface, the brazing material being introduced into saidpassages, and the brazing being done by placing the assembly of tube andblock into a furnace and keeping it for the required length of time atthe required temperature.

EDWARD (J. CHAPMAN. JOHN F. RANDALL.

